1. Field of the Invention
The present invention relates to the field of couplings, and more specifically, to driveline couplings having special utility in the marine industry.
2. Description of the Prior Art
In typical high performance boat applications, an engine is disposed in the boat, usually with an associated transmission and is coupled to a propeller driving shaft such that rotation of the driving shaft in the engine is transmitted to the propeller shaft thereby rotating the propeller. As the size and performance of such engine has increased, such as, for example, in high-performance or racing boats, the driveline coupling used to join the driveshaft with the propeller shaft has become extremely important. This is because to increase the efficiency of the boat it is helpful if all of the rotational energy of the driveshaft is transferred to the propeller shaft without such energy being lost. Because of the speed associated with such high preformance boats, and because of the general concern of safety, certain considerations must be taken into account in such driveline coupling which are generally not considered in other technologies. For example, it is know in the art that should the propeller shaft be loosened from the coupling, the propeller shaft could slide out of the boat during deacceleration and impinge upon the rudder. This has been known to cause not only a lack of speed but a loss of control of the boat which can result in destruction of the boat and harm to the occupants. However, early couplings were at odds with the safety factors in that it was found that an efficient means of coupling the prop shaft to the driveshaft was via a coupling whose safety considerations were not as extensive.
A typical shaft for coupling the driveshaft of an engine to the propeller shaft is disclosed by Coffing, U.S. Pat. No. 2,678,840. In Coffing, the propeller shaft is adapted to be received in the bore end of a hub member with the hub abutting a coupling plate. The hub is provided with axially extending keyways. Each of these keyways terminates short of the end of the shaft, the length conforming to the length of keys to be received therein so that the keys will be retained against axial displacement by the end of the keyways. The hub is provided with axial slots such that it can be coupled to the power shaft. A nut or other similar locking member is screwed onto the hub and is circumferentially disposed about the key. It should be noted, however, that such coupling device requires various sections to be gouged of the end of the propeller shaft which can have a tendency to weaken such shaft. In addition, complicated tooth locking members and associated keying members must be slip-fitted about the end of the propeller shaft. Finally, such shaft coupling does not take into consideration the longitudinal force associated with high performance boat couplings. That is, while such shaft coupling of Coffing may be sufficient to couple the prop shaft with the drive shaft in such a manner that rotation of the drive shaft causes the prop shaft to rotate, when the prop shaft is caused to deaccelerate quickly, such that there is a force vector along the length of the driveshaft, such coupling is not specifically designed to prevent the prop shaft from pulling out of the shaft coupling. This is a severe limitation, and as discussed hereinabove, should the prop shaft extend out from the boat, it could impinge upon the propeller and cause the aforementioned serious problems.
Other types of couplings are disclosed by Gredell, U.S. Pat. No. 2,585,113, Crowell, U.S. Pat. No. 281,618 and Swain, U.S. Pat. No. 140,600. These latter references, while being directed to shaft couplings, are not specifically designed or any way related to means for preventing both radial and longitudinal motion of the prop shaft such that retention of the prop shaft in the coupling is efficiently and safely maintained.
Thus, the prior art couplings, while they may be effective for coupling two shafts together, are of limited utility when the considerations are to prevent both longitudinal and undesirable radial rotation of the prop shaft especially during deacceleration thereof. The present invention provides an advancement in the art of shaft couplings and contains none of the aforementioned shortcomings associated with the prior art couplings. The present invention provides a flanged member and a coupling plate sandwiched between said flanged member and the boat's driveshaft, which solves the problem of permitting an efficient transfer of the energy from the driveshaft to the prop shaft but retains the prop shaft in such coupling even during rapid deacceleration of the prop shaft and boat.